The first step in simplifying this expression is to identify which, if any, terms can be combined. Remember, only like terms — constant terms or terms with the same variables and the same exponents — can be combined.
xy + x^2 + 2xy + y^2 - 3x^2
In this case, we have two xy-terms, two x^2-terms, and a y^2-term. Only the xy-terms and x^2-terms can be combined, so to simplify the expression we will rearrange it according to the Commutative Property of Addition and then evaluate the difference between the like terms.
